"As for heading straight for the building where my ‘informant’ claims the mutant is dreaming, I’m not tempted at all. Whether or not the information is genuine, I doubt very much that I’ve received the tip-off in any but an insignificant portion — technically, a set of measure zero — of the worlds caught up in the whirlpool. Any action taken only in such a sparse set of worlds would be totally ineffectual, in terms of disrupting the flow.

If I’m right, then of course it makes no difference what I do; if all the versions of me who received the tip-off simply marched out of the whirlpool, it would have no impact on the mission. A set of measure zero wouldn’t be missed. But my actions, as an individual, are always irrelevant in that sense; if I, and I alone, deserted, the loss would be infinitesimal. The catch is, I could never know that I was acting alone.

And the truth is, versions of me probably have deserted; however stable my personality, it’s hard to believe that there are no valid quantum permutations entailing such an action. Whatever the physically possible choices are, my alter egos have made — and will continue to make — every single one of them. My stability lies in the distribution, and the relative density, of all these branches — in the shape of a static, pre-ordained structure. Free will is a rationalisation; I can’t help making all the right decisions. And all the wrong ones."